Cathode mixture, cathode, and all-solid-state lithium ion secondary battery, and method for manufacturing the same

Abstract

A method is provided where an anode of an all-solid-state lithium ion secondary battery is easily doped with lithium and to provide a small resistance at a low battery capacity. The method includes a manufacturing method of a cathode including mixing at least a conductive assistant (C1) and a sulfide solid electrolyte (E1) to obtain a mixture; and mixing at least one cathode active material, a solid electrolyte (E2) and the mixture obtained from the first step to obtain a cathode mixture, wherein an amount of energy added to the sulfide solid electrolyte (E1) is larger than an amount of energy added to the solid electrolyte (E2), and the mixture is a material that releases lithium ions at a potential lower than a potential at which the cathode active material releases and occludes lithium ions. Manufacturing methods for a cathode and an all-solid-state lithium ion secondary battery including the cathode mixture are also disclosed.

The invention claimed is: 
     
       1. A method for manufacturing a cathode mixture comprising:
 a first step of mixing at least a conductive assistant (C1) and a sulfide solid electrolyte (E1) to obtain a mixture; and 
 a second step of mixing at least a cathode active material, a solid electrolyte (E2) and the mixture of the first step to obtain a cathode mixture, 
 
       wherein energy added to the sulfide solid electrolyte (E1) in the first step is larger than energy added to the solid electrolyte (E2) in the second step, and the mixture obtained in the first step is a material that releases lithium ions at a potential lower than a potential at which the cathode active material releases and occludes lithium ions. 
     
     
       2. The method for manufacturing a cathode mixture according to  claim 1 , wherein in the first step, the conductive assistant (C1) and the sulfide solid electrolyte (E1) are mixed by a ball mill. 
     
     
       3. The method of  claim 2 , where the ball mill adds said energy to the sulfide solid electrolyte (E1). 
     
     
       4. The method for manufacturing a cathode mixture according to  claim 1 , wherein in the second step where the cathode mixture has a solid content of from 1.7 mass % to 9.2 mass % based on entirety of the cathode mixture as 100 mass %. 
     
     
       5. The method for manufacturing a cathode mixture according to  claim 1 , wherein in the first step, the sulfide solid electrolyte (E1) in an amount of from 200 pts. by mass to 1600 pts. mass is mixed per 100 pts. by mass of the conductive assistant (C1). 
     
     
       6. The method for manufacturing a cathode mixture according to  claim 1 , wherein in the second step, a sulfide solid electrolyte (E3) is used as the solid electrolyte (E2). 
     
     
       7. The method for manufacturing a cathode mixture according to  claim 1 , wherein in the second step, a conductive assistant (C2) and a binder are further mixed, with the cathode active material, the solid electrolyte (E2) and the mixture obtained from the first step. 
     
     
       8. The method of  claim 1 , wherein the energy added to the sulfide solid electrolyte (E1) in the first step is by a mechanical mixing, and the energy added to the cathode active material, solid electrolyte (E20 and the mixture obtained from the first step is by mechanical mixing. 
     
     
       9. The method of  claim 1 , wherein said sulfide solid electrolyte (E1) comprises Li. 
     
     
       10. The method of  claim 1 , wherein said cathode active materials comprises Li. 
     
     
       11. The method of  claim 1 , wherein said solid electrolyte (E2) comprises Li. 
     
     
       12. A method for manufacturing a cathode comprising arranging the cathode mixture manufactured by the method according to  claim 1 , onto a surface of a cathode current collector. 
     
     
       13. The method for manufacturing a cathode according to  claim 12 , comprising:
 obtaining a cathode mixture paste that includes the cathode mixture and a solvent; and 
 applying the cathode mixture paste on the surface of the cathode current collector and drying the cathode mixture paste, to form a cathode mixture layer on the surface of the cathode current collector. 
 
     
     
       14. A method for manufacturing an all-solid-state lithium ion secondary battery comprising:
 stacking the cathode manufactured by the method according to  claim 12 , a solid electrolyte layer including at least a solid electrolyte, and an anode including at least an anode active material. 
 
     
     
       15. The method for manufacturing an all-solid-state lithium ion secondary battery according to  claim 14 , wherein the anode active material is constituted from one or more materials selected from the group consisting of silicon, silicon alloy, carbon, aluminum, aluminum alloy, tin and tin alloy.